IGBT and GaN Hybrid Half-Bridge Applications Based on Multi-Sampling Technology Considering Cost, Efficiency and Transient Performance

This paper presents a hybrid half-bridge structure based on GaN and IGBT devices, in which the IGBT branch operates at low frequency and contributes the entire average output current, while the average current of the GaN branch is zero, which allows GaNs to work at very high frequency even under heavy loads. Moreover, IGBT and GaN branchs contain opposite low-frequency ripple currents, therefore, the output current only contains the the average current of the IGBT branch and high-frequency part of the GaN branch, which combins the advantages of GaN and IGBT devices. In addition, since the system transient response is determined by the IGBT branch, and its low operating frequency limits the system bandwidth. In this paper, the multi-sampling technique is used to improve the transient performance. The simulation and experimental platforms are built and tested to verify the theoretical analysis. Results show that the GaN devices can maintain switching frequency 20 times higher than that of IGBTs over the entire load range. The drawback of more losses introduced by the GaN branch at light load can be improved by using phase shedding control. And the multi-sampling technology can decrease output voltage overshoot by 25% and may even more by increasing the sampling frequency of IGBT branch current.